Brewing and wine-making are ancient arts practiced centuries before the science of chemistry was born. The biochemistry of wine-making was demonstrated in 1856 by Louis Pasteur when he showed that wine is produced when the simple sugars in the fruit juices are fermented by yeast, namely Saccharomyces cerevisiae to yield ethanol and carbon dioxide. It is now known that alcoholic fermentation can be expressed by a series of enzyme-catalyzed biochemical reactions.
Beer is made in a similar manner by the fermentation of the carbohydrates present in cereal grains such as barley. These carbohydrates, largely polysaccharides, are not degraded by the glycolytic enzymes in yeast cells, which can only act on disaccharides and monosaccharides. To overcome this problem, the barley is "malted." In malting, the cereal seeds are allowed to germinate until they form the appropriate enzymes required to break down the polysaccharides of the cell walls as well as the starch and other polysaccharide food reserves within the cells of the seeds. Germination is then stopped by controlled heating. The malt, which now contains enzymes such as alpha amylase and maltase that are capable of breaking down the starch to maltose, glucose and other simple sugars, is formed into a "wort" by mixing the malt with water and mashing. This allows the enzymes to break down the cereal polysaccharides into the simple sugars which are soluble in the liquid medium. The remaining cell matter is then separated and the liquid wort boiled with hops to provide flavor. The liquid wort is removed from the kettle and subjected to filtration, such as by whirlpooling, to remove solid material, such as the trub-pile. The filtered liquid is then placed in a fermentor where yeast cells are added. In the presence of oxygen, the yeast cells are "activated", i.e., grow and reproduce very rapidly. Under anaerobic conditions, the yeast ferments the sugars into ethanol and carbon dioxide. After the fermentation has been stopped, the cells are removed and the raw beer is ready for final processing (e.g., adjustment of the amount of "head", CO.sub.2 concentration, concentration of flavorings, etc).
Carrageenan is added to the wort to improve beer clarification by removing suspended proteins in the trub pile. The addition of carrageenan to the wort also provides other advantages including the formation of a denser cold break (i.e., after fermentation), and shortened fermentation time.
The use of carrageenan in wort clarification can have drawbacks. Carrageenan can have very limited solubility in hot wort. Thus, carrageenan often balls-up when added to hot wort and forms "fish eyes", i.e., clumps of carrageenan and/or protein residues. Furthermore, this clarification process can make a mess in the kettle by creating large balls and gumming up the inside of the kettle. The carrageenan, due to the limited solubility, is not effectively removed in the filtration step and can contribute to the formation of a Krausen ring during fermentation. This clarification process can also result in more gelatinous hot wort break (i.e., when the wort is removed from the kettle). The gelatinous hot wort break in turn results in higher loss of wort in the hot trub and/or a denser cold break which reduces the speed of filtration of the cold wort when carrageenan is added. In addition, because the trub-pile that is formed by the current method is gelatinous, it tends to clog up a filter and reduce the life of a filter.
Therefore, there is a need for a method for clarifying beer that retains all the advantages of the current method but also provides tighter trub-pile formation to facilitate filtration, reduce the amount of wort loss, and to increase the life of a filter.